Merge tag 'pidfd-v5.2-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux

Pull pidfd updates from Christian Brauner:
 "This patchset makes it possible to retrieve pidfds at process creation
  time by introducing the new flag CLONE_PIDFD to the clone() system
  call. Linus originally suggested to implement this as a new flag to
  clone() instead of making it a separate system call.

  After a thorough review from Oleg CLONE_PIDFD returns pidfds in the
  parent_tidptr argument. This means we can give back the associated pid
  and the pidfd at the same time. Access to process metadata information
  thus becomes rather trivial.

  As has been agreed, CLONE_PIDFD creates file descriptors based on
  anonymous inodes similar to the new mount api. They are made
  unconditional by this patchset as they are now needed by core kernel
  code (vfs, pidfd) even more than they already were before (timerfd,
  signalfd, io_uring, epoll etc.). The core patchset is rather small.
  The bulky looking changelist is caused by David's very simple changes
  to Kconfig to make anon inodes unconditional.

  A pidfd comes with additional information in fdinfo if the kernel
  supports procfs. The fdinfo file contains the pid of the process in
  the callers pid namespace in the same format as the procfs status
  file, i.e. "Pid:\t%d".

  To remove worries about missing metadata access this patchset comes
  with a sample/test program that illustrates how a combination of
  CLONE_PIDFD and pidfd_send_signal() can be used to gain race-free
  access to process metadata through /proc/<pid>.

  Further work based on this patchset has been done by Joel. His work
  makes pidfds pollable. It finished too late for this merge window. I
  would prefer to have it sitting in linux-next for a while and send it
  for inclusion during the 5.3 merge window"

* tag 'pidfd-v5.2-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux:
  samples: show race-free pidfd metadata access
  signal: support CLONE_PIDFD with pidfd_send_signal
  clone: add CLONE_PIDFD
  Make anon_inodes unconditional

init/Kconfig

@@ -1171,9 +1171,6 @@ config LD_DEAD_CODE_DATA_ELIMINATION
 config SYSCTL
 	bool
 
-config ANON_INODES
-	bool
-
 config HAVE_UID16
 	bool
 
@@ -1378,14 +1375,12 @@ config HAVE_FUTEX_CMPXCHG
 config EPOLL
 	bool "Enable eventpoll support" if EXPERT
 	default y
-	select ANON_INODES
 	help
 	  Disabling this option will cause the kernel to be built without
 	  support for epoll family of system calls.
 
 config SIGNALFD
 	bool "Enable signalfd() system call" if EXPERT
-	select ANON_INODES
 	default y
 	help
 	  Enable the signalfd() system call that allows to receive signals
@@ -1395,7 +1390,6 @@ config SIGNALFD
 
 config TIMERFD
 	bool "Enable timerfd() system call" if EXPERT
-	select ANON_INODES
 	default y
 	help
 	  Enable the timerfd() system call that allows to receive timer
@@ -1405,7 +1399,6 @@ config TIMERFD
 
 config EVENTFD
 	bool "Enable eventfd() system call" if EXPERT
-	select ANON_INODES
 	default y
 	help
 	  Enable the eventfd() system call that allows to receive both
@@ -1516,7 +1509,6 @@ config KALLSYMS_BASE_RELATIVE
 # syscall, maps, verifier
 config BPF_SYSCALL
 	bool "Enable bpf() system call"
-	select ANON_INODES
 	select BPF
 	select IRQ_WORK
 	default n
@@ -1533,7 +1525,6 @@ config BPF_JIT_ALWAYS_ON
 
 config USERFAULTFD
 	bool "Enable userfaultfd() system call"
-	select ANON_INODES
 	depends on MMU
 	help
 	  Enable the userfaultfd() system call that allows to intercept and
@@ -1600,7 +1591,6 @@ config PERF_EVENTS
 	bool "Kernel performance events and counters"
 	default y if PROFILING
 	depends on HAVE_PERF_EVENTS
-	select ANON_INODES
 	select IRQ_WORK
 	select SRCU
 	help